The unit equal to one nautical mile per hour and used to measure wind speed is the knot.
One knot is exactly one nautical mile per hour, or 1.852 kilometers per hour. It is widely used in meteorology, maritime navigation, and aviation because nautical miles connect naturally with latitude: one nautical mile is approximately one minute of latitude. Wind forecasts, marine reports, and aircraft speeds therefore commonly use knots rather than ordinary miles per hour.
The unit originated with the chip log, a maritime device used from the era of sailing ships to estimate speed. A wooden float was towed behind a vessel while a line with regularly spaced knots ran out during a timed interval. Sailors counted the knots that passed their hands to estimate the vessel’s speed.
A knot is already a rate of speed, so “knots per hour” is generally incorrect when reporting speed; it would describe a change in speed, or acceleration. The standard symbol is “kn,” although “kt” is also common, especially in aviation.